Brucella abortus RNA Ccontributes to the Down Modulation of MHC II Eexpression on Monocytes/Macrophages Diminishing CD4 T cell Responses

MILILLO, MA; MARIN FRANCO, JL; GENOULA, M; GIAMBARTOLOMEI, GH; SERAFINO, A; ALCAIN, J; COSTA OLIVEIRA, S; TROTTA, A; MARINHO, FV; BALBOA, L; BARRIONUEVO, P

San Miguel de Tucuman

Congreso; LXVII Reunión Anual de la Sociedad Argentina de Inmunología (SAI); 2019

In order to persist inside the host, B. abortus must trigger different strategies to evade the adaptive T cell response. Previously, we demonstrated that B. abortus inhibits the IFN-γ-induced MHC-II surface expression on human monocytes. Consequently, the infected macrophages show a diminished antigen presentation to TCD4+ lymphocytes. B. abortus outer membrane lipoproteins ?bacterial structural components- are involved in MHC-II down-modulation through IL-6 secretion. Nevertheless, this phenomenon was less marked than that observed in the infection. This led us to think that there should have been another component associated to live bacteria implicated in MHC-II down-modulation. Actually, we have recently showed that B. abortus RNA, a PAMP associated to bacterial viability (vita-PAMP), is responsible for MHC-I down-modulation. Thus, the aim of this study was to analyse whether B. abortus RNA could also contribute to MHC-II down-modulation. For this, human monocytic THP-1 cells were incubated with B. abortus RNA in the presence of IFN-γ for 48 h. MHC-II expression (HLA-DR) was evaluated by flow cytometry. B. abortus RNA significantly (p